1. Field of the Invention
The present invention relates to a binocular telescope having a right telescopic optical system and a left telescopic optical system which can be moved rightward and leftward relative to each other, so that the interpupillary distance can be adjusted.
2. Description of the Related Art
Conventionally, in the binocular telescope described above, the right and left telescopic optical systems are mounted on right and left slide plates, which are partially overlapped, so that the right and left slide plates can slidably move rightward and leftward. Namely, by moving the right and left slide plates rightward and leftward relative to each other, the distance between the optical axes of the right and left telescopic optical systems, i.e., the interpupillary distance, is adjusted.
In such a binocular telescope with an interpupillary distance adjusting mechanism using slide plates (hereinafter referred to as a slide-type binocular telescope), when performing a focusing operation for the right and left telescopic optical systems, it is necessary to move a part of each of the right and left telescopic optical systems along the optical axis. For example, an erecting prism system and an ocular lens system must be moved relative to an objective lens system.
In this case, a right mount plate for supporting a part of the right telescopic optical system, or the erecting prism system and the ocular lens system, for example, is disposed on the right slide plate, and the objective lens system is disposed at a stationary position on the right slide plate, so that the right mount plate is moved along the optical axis relative to the objective lens whereby the right telescope optical system focuses. Similarly, a left mount plate for supporting the erecting prism system and the ocular lens system of the left telescopic optical system is disposed on the left slide plate, and the objective lens system is disposed at a stationary position on the left slide plate, so that the left mount plate is moved along the optical axis relative to the objective lens whereby the left telescope optical system focuses.
Further, in the binocular telescope, the focusing operations of the right and left telescope optical systems must be performed simultaneously, which means that the right and left slide plates must be moved along the optical axes of the right and left telescopic optical systems in synchronization with each other.
As may be understood from the above, to give an interpupillary distance adjusting function and a focusing function to the slide-type binocular telescope, a very complex mechanism has to be housed in the casing of the binocular telescope. Usually, if a complex mechanism is bulky, the binocular telescope has a tendency to become large. However, a binocular telescope system is required to be compact. Further, the compact design has to be attained without added cost.